1. Field of the Invention
This invention relates to a tape feeder for intermittently advancing a tape containing electronic parts by means of a tape-advancing mechanism driven by a driving member which moves in a reciprocating manner, thereby positioning each electronic part at a predetermined takeout position.
2. Prior Art
A tape feeder of this kind is disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 5-90786. According to the prior art tape feeder employed in an automatic electronic parts-mounting apparatus, the tape-advancing mechanism of the tape feeder operates in the following manner: As a rod is driven for vertical reciprocating motion, a swing lever is detachably engaged with the rod and driven thereby for performing swinging motion. The swinging motion of the swing lever is transmitted to an advancing lever by way of a transmission lever, and the advancing lever moves an advancing pawl to rotate a sprocket via an advancing gear in engagement with the advancing pawl, thereby advancing a tape. In stopping the advancing or feeding of the tape, the advancing pawl is caused to abut a feed stopper, whereby the tape is positioned at a predetermined location.
The reason for positioning the tape by bringing the advancing pawl into abutment with the feed stopper is as follows: Usually, a plurality of tape feeders, which are optionally replaceable, are arranged in parallel with each other at a parts-feeding block of the automatic electronic parts-mounting apparatus. Therefore, even if the tape is to be positioned according to a lower limit position of the rod which performs the vertically reciprocating motion, the advancing pawl is not necessarily stopped at a predetermined point where it should be stopped due to variation in the lower limit position of each rod and variation in the position and operation of the other component parts of each tape feeder. To overcome this inconvenience, the advancing pawl is forcedly stopped. The vertically reciprocating rod is displaced downward by way of a spring, and hence its downward movement can be absorbed wherever the tape-advancing motion of the tape-advancing mechanism of the apparatus may be stopped.
In the proposed tape feeder, the rod is driven by a cam for reciprocating motion, which is rotated in synchronism with intermittent rotation of a rotary table of the automatic electronic parts-mounting apparatus. At a point where the rod strikes the swing lever, the rod is moving downward at a fairly high speed, so that striking of the rod against the swing lever causes a shock and vibrations to the tape-advancing mechanism, which adversely affects the parts feeding operation of the tape feeder.
Further, the limit of feed or advance of the tape for positioning the chip is set by the stopper which the advancing pawl abuts to stop the tape-advancing operation in a forced manner. When the tape-advancing operation is about to be stopped, the tape-advancing mechanism is operating at a fairly high speed with inertia, and then the tape-advancing operation is suddenly stopped. Therefore, even if the downward movement of the rod is absorbed or a shock caused thereby is softened by the spring, a shock or impact of the striking of the advancing pawl on the stopper is still large, so that the position or orientation of the electronic part contained in the tape can be made unstable, resulting in instability of the following operation of taking out or sucking the electronic part.
Further, recently, the speed of parts-mounting operation of a parts-mounting apparatus is getting higher and higher, and accordingly, the driving member strikes the swing lever at a higher speed and the advancing pawl abuts or strikes the stopper at a higher speed. This makes the above-described inconveniences too serious to ignore, because the shock resulting from the abutment or collision is increased in proportion to the second power of the speed increased, so that vibrations of the tape feeder, which are conventionally fully damped before the part is taken out or sucked from the tape, are also difficult to be damped.